Jesus asked this woman for a drink of water, but it wasn't water He was interested in. He wanted to give this woman eternal life.
God is the greatest giver there ever was. He lives to give. When He asks something of us we can be assured that it is only so He can multiply it and give it back to us.
God is not interested in the water we can give Him. We don't have anything to offer God that He doesn't already have. God wants us. And by asking us to give of our time and money or desires, He is really asking us to give ourselves.
Many people have walked away from God sad, like the rich young ruler because all they could think about was what they would have to give up (Mark 10:22). All of our achievements and possessions are nothing compared to what God offers us in exchange.
Just as Jesus turned this woman's attention toward what He had to offer her, we need to focus our attention on what the Lord has given us in Christ. He is no fool who gives up what he can not keep to receive what he cannot lose.