If I drink, I’ll be able to pray

I have a question. At the moment, I’m quite weak, although not sick. I know that if I drink small amounts on Yom Kippur, I’ll be able to pray in a synagogue. But if I don’t drink anything, I’ll be so weak, that I’ll just have to lie in bed all day. What’s better? Thank you

Any drinking on Yom Kippur, even in small quantities (less than the quantity that is punishable), is forbidden by the Torah law. Therefore, anyone who is not endangering his life by fasting, must fast, and has no sanction at all for eating or drinking. Thus, it is your obligation not to pray the whole day, so that you won’t have to transgress a Torah prohibition.

The only time that a person must eat or drink small quantities on Yom Kippur is when fasting will endanger his life. In that case only is it preferable to eat small portions (if possible) so as not to transgress a prohibition that involves cores (abscission of the soul), and not eat larger portions, which is a prohibition that entails cores.  

Shulchan Oruch, section Orach Chaim, ch. 612, §5