Though, you may obtain similar results using SNAT.
Traditional way (Wrong for VPS):
iptables -A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A FORWARD -s 10.8.0.0/24 -j ACCEPT
iptables -A FORWARD -j REJECT
iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE
iptables -A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A FORWARD -s 10.8.0.0/24 -j ACCEPT
iptables -A FORWARD -j REJECT
iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j SNAT --to-source
IMPORTANT NOTE: Where you have to replace with your Public VPS IP given to you.
Also, replace 'eth0' to veth0 or venet0 (IF Required). As, Network Interface could be different in some cases.