Shell Script: Login to Oracle DB and fetch data to variable

I have this shell script, which login to oracle database, select from a table and put the result on other variable

Username=User1
Password=Pass1
eval DatabaseName=db_tst

var1 = 1

Result=`sqlplus -silent $Username/$Password@$DatabaseName <<EOF 
whenever sqlerror exit sql.sqlcode
SET PAGESIZE 0 FEEDBACK OFF VERIFY OFF HEADING OFF ECHO OFF 
select to_char(RUN_DATE,'YYYY-MM-DD:hh24:mi:ss') from table1 where col1 = $var1;
EXIT;
EOF`

echo $Result

the problem is the variables that passed to the "Result" ($Username, $Password...etc ) it's values not recognized. it gave me this message:

ERROR: ORA-01017: invalid username/password; logon denied SP2-0306: Invalid option. Usage: CONN[ECT] [{logon|/|proxy} [AS {SYSDBA|SYSOPER|SYSASM}] [edition=value]] where <logon> ::= <username>[/<password>][@<connect_identifier>] <proxy> ::= <proxyuser>[<username>][/<password>][@<connect_identifier>] SP2-0306: Invalid option. Usage: CONN[ECT] [{logon|/|proxy} [AS {SYSDBA|SYSOPER|SYSASM}] [edition=value]] where <logon> ::= <username>[/<password>][@<connect_identifier>] <proxy> ::= <proxyuser>[<username>][/<password>][@<connect_identifier>] SP2-0157: unable to CONNECT to ORACLE after 3 attempts, exiting SQL*Plus

ERROR: The SQL Plus Command Failed.

And when write it's values manually, it's loged in and the Result variable get the needed value. However I don't want to write the values manually, it should be passed through variables