Tips on getting a bottle of vodka to last longer?

So I have limited income and I’m an alcoholic and I usually blow my pay which is very low before the middle of the month and I’m just wondering what he has any tips to getting a bottle to last a little longer. I mix all my drinks with soda and I drink the cheapest vodka you can find and I drink a lot. Just wondered if there’s a way to Keep me occupied longer between drinks without losing the buzz.?