I had this surgery on April 15th of this year and I can help you with your questions.
DO NOT drink out of a straw unless you know you can do it without swallowing air. It is almost always easier to drink liquids without a straw and not get air into the stomach.
For the sweats, I assume you are on a narcotic or even a non-narcotic pain medication to take the edge off any pain you are having. Taking these medicines, as well as undergoing anesthesia and an operation in general can cause your body to act weird. A culmination of all these things is most likely why you are experiencing sweats. The first 3 to 4 weeks your body will be continuing to adjust post op so unless you are experiencing very intense pain, or some emergency situation, assume your body is adjusting.
For the first 6 weeks post op of my operation I had weird things happen to my body (including sweats) which the doctor attributed to the operation.
As for foods, yogurt and jello is your friend. Also those nutritional drinks (ensure type drinks) are EXCELLENT sources of sustenance and nutrients. Don't forget you cannot have chocolate flavoring thought.
Soup broths were great as well. Yogurt, jello, and the nutrition drinks were all sweet and creamy and a nice salty soup broth was refreshing for me. After 2 to 3 weeks you will probably be able to tolerate thick liquids and solid-type liquids like noodles, mashed potatoes, gravies and the like. I bought an individual sized blender where I prepared all my meals until I was able to eat solids. I would mix fruits, some soft vegetables and other "soft" solids in it (even cereal sometimes) and eat that for my meals. I often would even eat what my family was eating (grilled chicken, vegetables, mac and cheese etc) and throw it all in that blender and eat that so I could feel somewhat normal at dinner time.
It is a long process, but it is worth it. Hang in there and don't give into the temptation to eat solid foods until your doctor gives you the ok. You will probably lose weight (I lost 25lbs) and you will probably feel hungry all the time but DON'T GIVE IN!!! Also keep in mind you wont be able to hold near as much stuff inside you as you could. I used to love eating large plates of food and filling myself up but not I can not eat so much as a "fist" sized amount of food with drink.
Take your time and good luck!