I’m not aware of any traditional taijiquan or Wing Chun practices that specifically cause one to feel drained of energy, but I’m wondering if perhaps there is just a semantic issue here about what you’re describing. Very early on in my taiji experience, I was pushing hands with my first taiji sifu and experienced something that may be similar. What I felt was that I was effectively stuck, or perhaps immobilized is a better way of putting it. In my case, I didn’t feel that I was lacking any energy, but I did feel unable to deploy it. It was as though any movement I made was so subtly countered that I had no opportunity to follow through. This was not an instance of joint locking or strong arm tactics, the contact was extremely light, and yet I couldn't move. I was bewildered, but my sifu just smiled. He also happened be be a Wing Chun practitioner, but I think this kind of skill is not limited to one art or the other; it’s just gongfu.
When I described this experience to some of my more skeptical friends, they thought I was exaggerating or embroidering, but I’ve seen descriptions of other taiji masters who had this ability to immobilize a push hands partner. In Bruce Kumar Frantzis’ brief profile of Yang Shouzhong during his 1977 Hong Kong visit, he relates how he was invited to attend a Saturday push hands class. After pushing with several of Yang’s students, Frantzis had a turn with Master Yang. “His power was significant, and he easily bounced me after I yielded. Then as I next attempted to yield, he held me fast, with only his palms, locking me up tight so that it was not possible to yield or move my limbs or body in any direction, or exert any kind of power against him, in any way. It was like being held by a magnet.” (The Power of Internal Martial Arts, p. 169)
I’ve done a rough translation of an account of a similar push hands experience in Yang Zhenji’s book. A delegation of Japanese Yang style practitioners came to Yongnian to “seek the source,” and were able to meet with Yang Zhenji, who shared some taiji information with them.
“Afterward, the group leader said, ‘Mr. Yang, let’s push a bit.’ Yang Zhenji said, ‘I can’t push, and haven’t been teaching tuishou.’ But this Japanese friend had come a great distance, wanting to enrich his understanding of the Yang family gongfu, and he just had to push hands with him. Yang Zhenji couldn’t decline, so there in the foyer of the hotel he joined him in fixed step push hands. After some back and forth, Yang Zhenji’s two hands were on his opponent’s wrist and arm, and the opponent wanted to apply some force. Yang Zhenji at once loosened (yi song), and completely swallowed (tun) the opponent’s jin. Yet more attempts to apply force were absorbed, without letting go or resisting (bu diu bu ding). The opponent wanted to advance but couldn’t; wanted to retreat but didn’t dare, and was completely unable to stir. This group leader was a taijiquan expert, and immediately understood that he couldn’t match the gongfu of his Yang opponent.” (Yang Chengfu Shi Taijiquan, pp. 232-233)