The adverbs 只管 and 尽管
These adverbs can be used in the same way, but they can also have different meanings.
The same meaning
The adverbs 只管 
and 尽管 have the same meaning “feel free”, “come on”.
A verb used as a predicate is placed after these adverbs.
and 尽管 have the same meaning “feel free”, “come on”.
A verb used as a predicate is placed after these adverbs.Examples
有什么事你只管告诉我，我会处理的
If anything happens, feel free to tell me. Then I’ll decide
yǒu shénme shì nǐ zhǐguǎn gēn wǒ shuō, wǒ huì chǔlǐ de
只管吃！
Come on, eat! Don’t be shy!
zhǐguǎn chī
如果想用那辆车，你就尽管用吧
If you need the car, feel free to use it
rúguǒ xiǎng yòng nà liàng chē, nǐ jiù jǐnguǎn yòng ba
如果有疑问就尽管和我联系
If you have any questions, feel free to ask me
rúguǒ yǒu yíwèn jiù jǐnguǎn hé wǒ liánxì
The other meaning of 只管
只管 also has the meaning "just".
Examples
他不理我，只管坐在那儿看电视
He isn’t paying any attention to me. He is just sitting and watching TV
tā bù lǐ wǒ, zhǐguǎn zuò zài nàr kàn diànshì
你洗盘子时，就只管洗你的盘子
When you wash the dishes, just wash your plate
nǐ xǐ pánzi shí, jiù zhǐguǎn xǐ nǐ de pánzi
The other meaning of 尽管
尽管 also has the additional meaning “despite”.
尽管 is placed either at the beginning of a sentence or at the beginning of the second part of a sentence.
The subject is often placed after 尽管, but sometimes the subject is placed before it.
Examples
尽管她有困难，她照样继续工作
She continues to work, despite the difficulties
jǐnguǎn tā yǒu kùnnán, tā zhàoyàng jìxù gōngzuò
她尽管年事渐高，仍然十分活跃
Despite her age, she is still very active
tā jǐnguǎn nián shì jiàn gāo, réngrán shífēn huóyuè
尽管 is often used in the 尽管…但是… and 尽管…可是… structures.
and 尽管…可是… structures.Examples
尽管她已尽心竭力，但是仍然找不到工作
Despite her earnest efforts, she could not find a job
jǐnguǎn tā yǐ jìnxīn jiélì, dànshì réngrán zhǎo bù dào gōngzuò