I would say stop buying sodas. If it isn't there, she can't drink it. Let her have them occasionally but make it clear they are a treat not a regular drink. Don't tell her this has been done to make her drink water, pretend you forgot to buy it or the store ran out. Then see what you can both come up with instead of sugary sodas.
Buy sparkling mineral water and create healthy sodas with your child using various fruit juices. Fruit juices straight are often too strong for a young child's taste, so mixing it with fizzy water makes it more like soda pop. If she really objects at the very sight of all fruit juices, use high-juice bottled cordials instead - she won't realize it's mainly fruit juice.
Let her be involved in the creative process and choose which juices to mix, so she feels positive toward the resulting drink. Maybe let her create a name for the new drink, maybe even put it into bottles and help her make labels. Make it like a game, a shared activity with her mom. Drink it yourself and show some enthusiasm. Other adults, such as her dad or grandparents, or your friends, can try the new drink your child has created and say how delicious it is.
Of course, many fruit juices are high in acid and excessive consumption of these can harm the tooth enamel. But from what you say, excessive consumption is unlikely since she is reluctant to drink much at all. What you need to do is wean her off sugary sodas (assuming that's what she drinks at present - you don't actually say). It's a step in the right direction.
Drink water yourself and let her see you doing so. Ditto the rest of the family. It's important to set an example. So many parents tell their kids to eat broccoli while they themselves tuck into French fries. Put a jug of iced water on the table at mealtimes.
While people don't like to give coffee to kids because of the caffeine, tea has a lot less caffeine so if your child likes it, that is one way of consuming water.
Kids never want to do what they are ordered/advised to do by their parents, even 7 year olds. Things that are "good for you" are by definition horrible. You need her to take her own decision to drink water.
Since she is only 7, maybe you could get her to explain to someone or something else - maybe a puppy or kitten - why it should drink water. She might convince herself at the same time.
You may be conning her if you do the above, but it's in a good cause:)