I had a lot of issues with Ensure when I was trying to gain weight and get nutrients in. They just taste absolutely awful to me and make me nauseous as well. I had a lot more luck with Boost, specifically the Peaches & Cream Boost and Strawberry. Vanilla is good too but I’m not a fan of chocolate so I never tried that one. You could also try making your own shakes at home and storing them in the fridge, with protein powder and other stuff you know you need! I’ve done that too and made myself
Oh also pro tip for weight gain, you can sneak heavy cream and avocado in a lot more dishes than you might think. Even sweet dishes you can mash some avocado in there, especially a lot of filipino desserts. I thank my weight gain success to avocado and heavy cream. Obviously different things work for different people but!